Who Discovered the Sun is a Star?

Helios the sun god

Introduction

In ancient Greece, early scientists such as Thales of Miletus (624-546 BC) first started to suspect that the Sun was not the deity Helios (Apollo) driving his chariot around the Earth, but was instead merely a round fiery ball hanging in space. In 450 BC, Greek philosopher Anaxagoras then became the first person we know of in history to suggest that the stars were actually other suns such as our own, but lying at such great distances that their heat could not be felt back here on Earth.

He too mistakenly believed that the Sun was a red-hot stone “bigger than the Peloponnese”. Of course, Anaxagoras could not prove his theories, which in any case were considered heretical, and so led to his banishment from Athens.

It wasn’t until two millennia later when the Scientific Revolution (1550-1700) gave way to the Enlightenment (1685-1815) that advancements in science and telescopes meant that the precise nature of the stars could be determined. Distances to the stars could also be calculated, in the process revealing that their brightness would indeed appear similar to the Sun if not for their vast distant locations.

In the mid-19th century, further scientific advancements in spectroscopy and photography, and with them the ability to measure the surface temperature and chemical composition of the Sun and stars, provided the definitive proof that the Sun was in fact just another star, after all.

Sun Worship In Ancient Times

Throughout history, people have looked upon the Sun as an all-powerful deity that provided light and heat to chase away the darkness and nourish and sustain the Earth’s inhabitants. Naturally, such an important supreme being commanded awe and respect.

In ancient Egypt, for instance, the falcon-headed Ra was worshiped as the king of the gods. Meanwhile, on the other side of the world the Aztec of Mesoamerica offered human sacrifices to Huitzilopochtli, their god of the Sun and war, who was depicted as a blue man wearing armor and a hummingbird feathered helmet.

In Hinduism, the world’s oldest existing religion and still practiced by over 80% of Indians, the Sun is still considered to be the deity and is associated with the god Surya, the dispeller of darkness.

Solar Deity In Ancient Greece

The ancient Greeks believed that the Sun was the god Helios, who each day would drive his fiery chariot across the sky. While astronomers such as Thales of Miletus (624-546 BC) began to realize that the Sun was not a deity, the transition towards a less superstitious and more scientific explanation of the Sun, planets, and stars was a slow one.

Even Plato notes in his Symposium that Socrates (469-399 BC) would greet the Sun each morning and offer prayers. Another reminder of the Sun’s enduring reverence in Greece was a Wonder of the Ancient World called the Colossus of Rhodes, which was a 33 meters high statue of the Greek titan-god Helios, whose twelve year long construction was eventually completed in 280 BC.

It is no surprise, then, that Greek philosopher Anaxagoras (500-428 BC) came under scrutiny from authorities after proposing that the Sun was not a supreme being at all, but a huge red-hot rock in space, similar to the stars that can be seen in the night sky.

Anaxagoras (500-428 BC)

AnaxagorasDuring the 5th century BC, a Greek philosopher named Anaxagoras, who hailed from Asia Minor, came to Athens where he introduced the idea of philosophy, which is the basis for our modern science. He described everything that existed as a mixture of imperishable, infinitely divisible elements, perhaps referring to atoms and molecules, and even postulated as to the possibility of extraterrestrial life.

Anaxagoras also correctly deduced and explained how eclipses occur, said that the Moon was not a luminous body, but rather that it glowed by the reflected light of the Sun. Furthermore, he attempted explanations for meteors, rainbows, and the Sun itself.

– Logic Behind Anaxagoras’ Theory

Anaxagoras postulated that the Sun was merely a stone that had been torn from the Earth and then ignited due to rapid spinning, and that all other heavenly bodies were similarly made of stone. As Anaxagoras was quoted as saying:

“Everything has a natural explanation. The moon is not a god but a great rock and the sun a hot rock.”

His theory may have been inspired by having witnessed a wagon sized meteorite falling from the sky near the Dardanelles in 467 BCE. Having examined the object, he concluded that meteorites were pieces of rock that had broken off from the Sun and fallen to Earth. Likewise, this confirmed to him that the stars and the Sun were one and the same—burning rocks, and that the same general rule applied throughout the Universe.

Having fallen foul of Athens impiety laws, Anaxagoras was sentenced to death, but survived by going into exile. He subsequently retired to the city of Lampsacus, where he taught to a more appreciative and respectful audience until his death in 428 BC.

The Renaissance Period (1300– 1700 AD)

Copernicus (1473-1543)

CopernicusAround 1800 years later, Copernicus (1473-1543) helped spark the Scientific Revolution by publishing his seminal work ‘De Revolutionibus’ in which he showed that the Earth was just another planet revolving around the Sun. In order to avoid persecution by the Catholic Church, Copernicus did so from his death-bed, and while efforts were made to withdrawn the book from circulation pending suitable corrections being made, there was already beginning to be widespread suspicions voiced across Europe that the Sun was merely a close star.

Giordano Bruno (1548-1600)

In 1584, Italian philosopher and Dominican friar, Giordano Bruno, published two important books in which he propounded the Copernican theory, and argued that if the planets circled the Sun and the Earth was simply another planet, then the Sun should not be considered anything particularly special. As he wrote at the time:

“The composition of our own star and world is the same as that of as many other stars and worlds as we can see.”

In other words, it seemed reasonable to him that the Sun was merely another star, and he subsequently made a distinction between “suns” which generate their own light and heat; and the “earths” and moons which revolve and are nourished and powered by them. One esteemed modern astrophysicist, Steven Soter, has even suggested that Bruno was the first person in history to truly grasp the concept that “stars are other suns with their own planets.”

Unfortunately, The Inquisition found Giordano Bruno guilty of heresy, and he was burned at the stake in 1600, but has since been recognized as a “martyr of science”.

Galileo Galilei (1564-1642)

Galileo and his telescopeIn 1609, Galileo Galilei pointed his recently invented primitive refractor telescope at the stars, and was then able to use Copernicus’s calculations to show that the planets, including the Earth, did revolve around the Sun.

No amount of magnification he could apply to his telescope, though, would allow Galileo to increase and resolve the size of a star into a perceptible “disk”. The stars are simply too far away, thus yielding few clues as to their nature. In fact, it would take almost another three centuries before the invention of the spectroscope would prove the precise scientific composition of these stellar bodies, and that the Sun is undoubtedly a star.

Astronomical Spectroscopy

In 1666, Isaac Newton showed that a prism separated white light into a spectrum of its constituent parts, rather than creating the rainbow colors that are seen. In 1802, William Wollaston then constructed a spectrometer which showed the Sun’s spectrum on a screen, but noted that there were dark bands of missing colors.

In 1814, Joseph von Fraunhofer invented the spectroscope and mapped 574 of these lines, after which a number of scientists helped advance the study of spectroscopy, including Gustav Kirchhoff and Robert Bunsen who in 1857 were able to establish a connection between chemical elements and their own individual spectral patterns.

Astronomical SpectroscopyFurther study revealed that each element absorbs light of a particular color, thus leaving a specific “signature” line. And after spectroscopes were coupled to telescopes, scientist were able to identify additional chemical elements, and work our the chemical composition of the stars, as well as distinguish between nebulae and galaxies in the night sky.

During this period, an Italian Jesuit priest and astronomer, Angelo Secchi (1818-1878), became a pioneer in the study of stellar spectroscopy, and through analysis of some 4,000 stellar spectrograms discovered that the stars came in a limited variety of types distinguishable by their unique spectral patterns. He subsequently devised the first stellar classification system, and is recognized as being one of the first scientists to definitively state that the Sun is a star.

What We Now Know About The Sun

We now know that the Sun is a yellow dwarf star composed of around 73% hydrogen, 25% helium, and 2% heavier elements, such as oxygen, carbon, neon, and iron. Its spectral class is GV2, with the G2 indicating a surface temperature of roughly 5505 °C (5778 K); and the V indicating that the Sun is an active star on the main sequence.

Related Articles